The day kicks off with our first glimpse of Usain Bolt running in a heat for the 100 meters. It’s appointment viewing anytime the world’s fastest man hits the track, but fans will be keeping an especially close eye on this one. Bolt injured his hamstring in the Jamaican world championships in July, and while he returned (and won) in late July, it will be interesting to see how he looks on the track in Rio. Allyson Felix will also be hitting that track in the heats for the 400.

Later that night is the main event: Michael Phelps’s final race in Rio. The most decorated Olympian of all time heading into Rio, Phelps will be going for his 23rdgold Saturday night in the men’s 4x100 medley relay. Could this be Phelps’s final race on the Olympic stage?

Here are a few other things to watch for on Saturday, with a full TV guide below that:

Women’s Tennis: Singles Gold Medal (2 p.m. ET, NBC)

Germany’s Angelique Kerber (the No. 2 seed) will face surprising upstart Monica Puig of Puerto Rico. Puig, the 37th seed in the draw, will be the country’s first female medalist in any sport and she has a chance to earn Puerto Rico’s first-ever gold. “This Olympics isn’t about me it’s about Puerto Rico,” Puig said, “and I know how bad they want this. This isn’t for me this is for them.”

Women’s 100 Meter (9:35 p.m. ET, NBC)

This is anyone’s race. Among the runners to watch: Jamaica’s Elaine Thompson (who ran a personal best, 10.70, in 2016); U.S.’s Tori Bowie (the bronze medalist in the 100 at last year’s world championship); and Jamaica’s Shelly-Ann Fraser-Pryce (the gold medalist at worlds, but an underdog now given her injury woes).

Rowing, Women's Eight (10 a.m. ET, NBC)

The U.S. women’s eight has won 10 straight world or Olympic titles. They are the heavy favorites for a third straight gold.